<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			#outer{
				width: 300px;
				height: 300px;
				border: 1px solid #333;
				background: yellowgreen;
				
				position: relative;
			}
			#middle{
				width: 200px;
				height: 200px;
				border: 1px solid #333;
				background: red;
				
				position: relative;
			}
			#inner{
				width: 100px;
				height: 100px;
				border: 1px solid #333;
				background: purple;
				
				position: absolute;
				left: 0px;
				top: 0px;
			}
		</style>
	</head>
	<body>
		<div id="outer">
			outer
			<div id="middle">
				middle
				<div id="inner">
					inner
				</div>
			</div>
		</div>
	</body>
</html>
